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Perfluoropolyether primary bromides and iodides are a family of highly useful and reactive chemicals that can be used, for example, as lubricants, surfactants, and additives for lubricants and surfactants. See, e.g., Journal of Fluorine Chemistry 1999, 93, 1 and 2001, 108, 147 (hereinafter “Brace”). Brace discloses addition of iodides to alkenes, alkynes, allyls, etc to produce secondary iodides that have limited uses. Brace does not disclose the synthesis of valuable primary perfluoropolyether iodides.
The Hundsdiecker reaction (Journal of Organic Chemistry 1967, 32, 833) deals with reacting silver salts of the perfluoroalkyl carboxylic acid with free iodine. Such a reaction involves expensive reagents and is of limited commercial utility. Journal of Fluorine Chemistry 1993, 65, 59 (hereinafter “Eapen”) discloses converting a hexafluoropropylene oxide (HFPO) tetramer acid fluoride to a secondary iodide. See also, U.S. Pat. Nos. 5,278,340 and 5,288,376 (halogen exchange of the fluorine in the acid fluoride with iodine using metal iodides and aprotic/polar solvent and exposing the acid iodide to ultraviolet irradiation, forming only the secondary iodide).
Journal of Fluorine Chemistry 1997, 83, 117 discloses exposing a molar excess of lithium iodide to low molecular weight perfluoroether acid fluorides at 180° C. for at least 6.5 hours to produce two low molecular weight perfluoropolyether iodides, one primary and one secondary.
U.S. Pat. No. 5,453,549 discloses a low molecular weight ethylene derivative of a primary iodide. It does not disclose the value of higher molecular weight products. Nor does it disclose the method of synthesis of the starting materials.
Journal of Fluorine Chemistry, 1990, 47, 163 discloses the feasibility of the formation of a primary iodide, in the gas phase, from dimer and trimer of hexafluoropropylene oxide.
While a polyfluorocarbon acid halide can likewise be converted to an iodide in a perhalogened solvent using iodine and a metal carbonate, U.S. Pat. No. 4,973,762, subsequent removal of the solvent can be expensive and undesired traces can be left behind.
Mono-functional (Φ-CF(CF3)CF2OCF(CF3)C(O)—F; Formula I) and di-functional (FC(O)CF(CF3)OCF2CF(CF3)-Φ′-CF(CF3)CF2OCF(CF3)C(O)F; Formula II) acid fluorides, which can be used in the present invention can be prepared according to Moore, U.S. Pat. No. 3,332,826 and Koike et al., U.S. Pat. No. 5,278,340 where Φ and Φ′ are respectively monovalent and divalent perfluoropolyether moieties. Additionally, other acid fluorides of Formulae I and II are the reaction products formed from the polymerization of hexafluoropropylene oxide alone or with suitable starting materials, 2,2,3,3-tetrafluorooxetane, or the photooxidation of hexafluoropropylene or tetrafluoroethylene.
Secondary iodides from said acid fluorides can be prepared, for example at 0–60° C. using radiation from a photochemical lamp (for instance a lamp with an ultra-violet light output in the wavelength range of 220–280 nm (U.S. Pat. No. 5,288,376)).
The usefulness of this invention is demonstrated, for example, by the reactions of primary perfluoropolyether iodides with bromobenzene which could lead directly to perfluoropolyether substituted bromobenzene without the use of toxic or pyrophoric chemicals such as sulfur tetrafluoride or butyl lithium. These functionalized perfluoropolyether (PFPE) intermediates are used to form readily soluble, high temperature additives for fluorinated oils in boundary lubrication, as disclosed in Eapen and U.S. Pat. No. 5,550,277. These primary bromides or iodides described herein can also be used as intermediates in the production of fluorous phase media for applications such as catalysis (Horváth, I., Acc. Chem. Res. 1998, 31, 641) or separations (Curran, D. P. Angew. Chem., Int. Ed. Engl. 1998, 37, 1174), fluorosurfactants, and mold release agents.
Because there are few useful perfluoropolyether primary bromides or iodides and processes for producing them are not readily available to one skilled in the art, there is an ever increasing need to develop such products and processes.